The servo turret is a complex electromechanical hydraulic component that is the most likely to fail in a numerical control lathe. Reliability evaluation is used to make statistical inferences about the reliability characteristics of products according to all the information related to product reliability. Failure data is the basis of reliability evaluation; however, it is very difficult to collect many accurate failure data for reliability evaluation. In this paper, the reliability of servo turret is evaluated based on failure data that contains accurate failure data and interval censored data. First, a mixture Weibull distribution is chosen for fitting the reliability model. Then, expectation-maximization algorithm is used for estimating the parameters of the distribution which contains hidden variable, and the confidence interval of parameters is constructed using the delta method. In the simulation, different percentages of accurate data and interval data are used and compared with data containing only accurate data. The accuracy of this method is evaluated by mean square error. Finally, the method is applied to the failure data of servo turret and the parameters of mixture Weibull distribution are determined. For possibly simplifying the mixed Weibull distribution, the hypothesis of shape or scale parameters being equal is tested. The hazard property and mean time between failure are then estimated and associated 95 % confidence intervals are obtained.

伺服转塔架是复杂的机电液压组件，在数控车床中最有可能发生故障。可靠性评估用于根据与产品可靠性有关的所有信息对产品的可靠性特征进行统计推断。故障数据是可靠性评估的基础；但是，很难收集许多准确的故障数据来进行可靠性评估。在本文中，基于包含准确故障数据和间隔检查数据的故障数据评估了伺服转塔的可靠性。首先，选择混合的威布尔分布来拟合可靠性模型。然后，使用期望最大化算法来估计包含隐藏变量的分布参数，用delta法构造参数的置信区间。在模拟中，使用不同百分比的准确数据和间隔数据，并将其与仅包含准确数据的数据进行比较。该方法的准确性由均方误差评估。最后，将该方法应用于伺服转塔的故障数据，确定混合威布尔分布的参数。为了可能简化混合的威布尔分布，测试了形状或比例参数相等的假设。然后估算危险特性和平均失效间隔时间，并获得相关的95％置信区间。该方法的准确性由均方误差评估。最后，将该方法应用于伺服转塔的故障数据，确定混合威布尔分布的参数。为了可能简化混合的威布尔分布，测试了形状或比例参数相等的假设。然后估算危险特性和平均失效间隔时间，并获得相关的95％置信区间。该方法的准确性由均方误差评估。最后，将该方法应用于伺服转塔的故障数据，确定混合威布尔分布的参数。为了可能简化混合的威布尔分布，测试了形状或比例参数相等的假设。然后估算危险特性和平均失效间隔时间，并获得相关的95％置信区间。